namei: remove restrictions on nesting depth (894bc8c4) · Commits · 戴 / test

fs/namei.c

+52 −14

Original line number	Diff line number	Diff line
		@@ -492,6 +492,7 @@ void path_put(const struct path *path)
		}
		EXPORT_SYMBOL(path_put);

		#define EMBEDDED_LEVELS 2
		struct nameidata {
		struct path path;
		union {
		@@ -509,9 +510,42 @@ struct nameidata {
		struct path link;
		void *cookie;
		const char *name;
		} stack[MAX_NESTED_LINKS + 1];
		} *stack, internal[EMBEDDED_LEVELS];
		};

		static void set_nameidata(struct nameidata *nd)
		{
		nd->stack = nd->internal;
		}

		static void restore_nameidata(struct nameidata *nd)
		{
		if (nd->stack != nd->internal) {
		kfree(nd->stack);
		nd->stack = nd->internal;
		}
		}

		static int __nd_alloc_stack(struct nameidata *nd)
		{
		struct saved p = kmalloc((MAXSYMLINKS + 1) sizeof(struct saved),
		GFP_KERNEL);
		if (unlikely(!p))
		return -ENOMEM;
		memcpy(p, nd->internal, sizeof(nd->internal));
		nd->stack = p;
		return 0;
		}

		static inline int nd_alloc_stack(struct nameidata *nd)
		{
		if (likely(nd->depth != EMBEDDED_LEVELS - 1))
		return 0;
		if (likely(nd->stack != nd->internal))
		return 0;
		return __nd_alloc_stack(nd);
		}

		/*
		* Path walking has 2 modes, rcu-walk and ref-walk (see
		* Documentation/filesystems/path-lookup.txt). In situations when we can't
		@@ -857,7 +891,7 @@ const char get_link(struct nameidata nd)
		if (nd->link.mnt == nd->path.mnt)
		mntget(nd->link.mnt);

		if (unlikely(current->total_link_count >= 40)) {
		if (unlikely(current->total_link_count >= MAXSYMLINKS)) {
		path_put(&nd->path);
		path_put(&nd->link);
		return ERR_PTR(-ELOOP);
		@@ -1789,22 +1823,18 @@ Walked:
		if (err) {
		const char *s;

		if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
		path_put_conditional(&nd->link, nd);
		path_put(&nd->path);
		err = -ELOOP;
		goto Err;
		err = nd_alloc_stack(nd);
		if (unlikely(err)) {
		path_to_nameidata(&nd->link, nd);
		break;
		}
		BUG_ON(nd->depth >= MAX_NESTED_LINKS);

		nd->depth++;
		current->link_count++;

		s = get_link(nd);

		if (unlikely(IS_ERR(s))) {
		err = PTR_ERR(s);
		current->link_count--;
		nd->depth--;
		goto Err;
		}
		@@ -1812,7 +1842,6 @@ Walked:
		if (unlikely(!s)) {
		/* jumped */
		put_link(nd);
		current->link_count--;
		nd->depth--;
		} else {
		if (*s == '/') {
		@@ -1842,7 +1871,6 @@ Walked:
		Err:
		while (unlikely(nd->depth)) {
		put_link(nd);
		current->link_count--;
		nd->depth--;
		}
		return err;
		@@ -1851,7 +1879,6 @@ OK:
		name = nd->stack[nd->depth].name;
		err = walk_component(nd, LOOKUP_FOLLOW);
		put_link(nd);
		current->link_count--;
		nd->depth--;
		goto Walked;
		}
		@@ -2055,7 +2082,11 @@ static int path_lookupat(int dfd, const struct filename *name,
		static int filename_lookup(int dfd, struct filename *name,
		unsigned int flags, struct nameidata *nd)
		{
		int retval = path_lookupat(dfd, name, flags \| LOOKUP_RCU, nd);
		int retval;

		set_nameidata(nd);
		retval = path_lookupat(dfd, name, flags \| LOOKUP_RCU, nd);

		if (unlikely(retval == -ECHILD))
		retval = path_lookupat(dfd, name, flags, nd);
		if (unlikely(retval == -ESTALE))
		@@ -2063,6 +2094,7 @@ static int filename_lookup(int dfd, struct filename *name,

		if (likely(!retval))
		audit_inode(name, nd->path.dentry, flags & LOOKUP_PARENT);
		restore_nameidata(nd);
		return retval;
		}

		@@ -2393,6 +2425,7 @@ filename_mountpoint(int dfd, struct filename name, struct path path,
		int error;
		if (IS_ERR(name))
		return PTR_ERR(name);
		set_nameidata(&nd);
		error = path_mountpoint(dfd, name, path, &nd, flags \| LOOKUP_RCU);
		if (unlikely(error == -ECHILD))
		error = path_mountpoint(dfd, name, path, &nd, flags);
		@@ -2400,6 +2433,7 @@ filename_mountpoint(int dfd, struct filename name, struct path path,
		error = path_mountpoint(dfd, name, path, &nd, flags \| LOOKUP_REVAL);
		if (likely(!error))
		audit_inode(name, path->dentry, 0);
		restore_nameidata(&nd);
		putname(name);
		return error;
		}
		@@ -3288,11 +3322,13 @@ struct file do_filp_open(int dfd, struct filename pathname,
		int flags = op->lookup_flags;
		struct file *filp;

		set_nameidata(&nd);
		filp = path_openat(dfd, pathname, &nd, op, flags \| LOOKUP_RCU);
		if (unlikely(filp == ERR_PTR(-ECHILD)))
		filp = path_openat(dfd, pathname, &nd, op, flags);
		if (unlikely(filp == ERR_PTR(-ESTALE)))
		filp = path_openat(dfd, pathname, &nd, op, flags \| LOOKUP_REVAL);
		restore_nameidata(&nd);
		return filp;
		}

		@@ -3306,6 +3342,7 @@ struct file do_file_open_root(struct dentry dentry, struct vfsmount *mnt,

		nd.root.mnt = mnt;
		nd.root.dentry = dentry;
		set_nameidata(&nd);

		if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN)
		return ERR_PTR(-ELOOP);
		@@ -3319,6 +3356,7 @@ struct file do_file_open_root(struct dentry dentry, struct vfsmount *mnt,
		file = path_openat(-1, filename, &nd, op, flags);
		if (unlikely(file == ERR_PTR(-ESTALE)))
		file = path_openat(-1, filename, &nd, op, flags \| LOOKUP_REVAL);
		restore_nameidata(&nd);
		putname(filename);
		return file;
		}

include/linux/namei.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -11,6 +11,8 @@ struct nameidata;

		enum { MAX_NESTED_LINKS = 8 };

		#define MAXSYMLINKS 40

		/*
		* Type of the last component on LOOKUP_PARENT
		*/

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